A model of p, p′-DDE and total PCB bioaccumulation in birds from the Southern California Bight

Abstract

Pathways of p, p′-DDE and PCB transfer to three species of birds were characterized as part of the Southern California Bight Natural Resource Damage Assessment. Based upon analysis of the results of extensive field studies conducted by other investigators to characterize the dietary composition, foraging behavior, and contaminant levels in the predators and in their prey, 70–80 percent of the contaminant dose received by the peregrine falcon and 90–95 percent of the dose to the bald eagle originated within the Bight. Dynamic, mechanistic, bioenergetics-based bioaccumulation models for p, p′-DDE and PCBs were developed for both species. Measured contaminant levels in predator eggs were found to be quantitatively consistent with measured levels in their prey, providing support for the estimates of dietary composition and foraging behavior, and therefore for the characterization of contaminant sources. Based on the model, most of the contaminant dose to the bald eagles on Santa Catalina Island is accumulated from sea lion carrion, and, based on a model of female sea lion bioaccumulation described in a companion publication, much of the dose to the sea lion originates in the more highly contaminated regions of the Bight which include the Palos Verdes Shelf and Santa Monica Bay. The importance of non-local contaminant sources to the eagle was surprising, since the eagles are non-migratory and forage locally on Santa Catalina, and consume 90 percent fish, most of which are nearshore species. A third model constructed for the double-crested cormorant indicated that cormorants from Anacapa Island are likely to feed to some degree in the more highly contaminated regions of the Bight near the Palos Verdes Shelf. In contrast, the cormorants from Santa Barbara Island probably feed less intensively in the more contaminated regions of the Bight than previously thought. The model framework developed here is generally applicable. It can aid in predicting the course of natural recovery and the impacts of remediation activities, and can provide quantitative exposure estimates for use in risk assessment.